Automatic glass cutting machines have been proposed which utilize a scanning head equipped with an emitter of X pulses representing the X coordinates of the various points on a pattern and an emitter of Y pulses representing the Y coordinates of the various points on a pattern representing the outline to be cut and where the scanning head is guided along the pattern to register a program. These X and Y pulses constitute signals representing the outline to be cut and they are stored in memory. Thereafter, the memory need only be recalled in order to control the cutting machine.
Published French patent application No. 2,367,710 describes such a glass sheet cutting machine controlled by a magnetic tape carrying information on the X and Y coordinates of the various points on the outline to be cut. A similar cutting machine of this type may also be used to record the cutting program on the magnetic tape and is described in German patent application No. 2,646,053.
U.S. patent application 092,972 filed Nov. 9, 1979 Pat. No 4,325,188 describes a device for recording a cutting program intended for such a cutting machine. In such a device, the scanning head follows the outline of a pattern with the aid of a sensor. Theoretically, when the scanning head has traversed the entire outline of the pattern, it will have returned to the point it started from when beginning the scanning operation. In practice, whether the scanning head is run manually or automatically controlled, this is not quite true, and there is a slight discrepancy between the starting point and the end point of the scan. If the starting point, or zero point, is not precisely reached after the scan, this will be reflected in the recorded program by a deviation between the starting index and the target index. When the recorded program is operated to guide the cutting machine, this slight deviation is represented, on a cut sheet taken individually, by an insignificant jog in the cut, on the order of 0.1 mm, and not even noticeable to the naked eye. But since the target point of the cutting head is at the same time its starting point for the next cut, these discrepancies accumulate with each operation of cutting another sheet of glass, so that eventually the cutting tool is carried beyond the edges of a sheet of glass out of which a part is to be cut.
It is therefore an object of our invention to provide a method and a device for correcting the control program of an automatic glass cutting machine so that in the recorded program, the index corresponding to the starting point of a closed line of cut is exactly the same as the index corresponding to the target point after the line of cut has been traversed.